Spontaneous Aerobic Oxidation of 1,1,2,2-Tetrakis(N-methylpyridin- 4-ium)ethane Iodide to the Alkene and the Epoxide

Abstract

The tetrapyridinium salt 1 was found to undergo quantitative air oxidation upon dissolving it in water. The corresponding alkene and the epoxide were found as the only products of the oxidation. A mechanism that involves an alkyl hydroperoxide intermediate 1″ undergoing a transformation that yields both products is proposed. Air oxidation of 1 shows the potential of the acceptor substituted alkanes to be used in the studies of mostly unknown direct epoxidation of single C-C bonds.

Aerobic Oxidation of in Situ Generated Cyanine Dyes Leading to DNA Damage

“…Comparison of the superoxide reduction potential and theoretically predicted oxidation potential of 4′ also supports the exergonicity of the oxidation . The proposed mechanism of the aerobic oxidation of 4 is similar to the mechanism of the oxidation of 1 . Due to the challenge in isolation of 4′ ′ , 1 H NMR was utilized to observe its formation.…”

“…Recently, we described a spontaneous thermal aerobic oxidation of the salt 1 . This reaction proceeded through the formation of oxygen-sensitive monomethine cyanine dye dimer 1′ that spontaneously transforms into 2 and 3 .…”

“…During our previous study, an unexpected and rare transformation from alkane to epoxide and alkene occurred after water was added to 1 in air . Intrigued by this discovery, we synthesized 4 as an iodide salt and investigated its behavior in water solutions exposed to air.…”

“…A positive result of a classical iodine–starch peroxide test also supported the formation of 4′′ . We showed previously that the outcome of the oxidation of 1 does not depend on the type of the counterion (iodide vs BF 4 – ) …”

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…However, direct synthesis of an epoxide from an alkane is not often possible, as it require high temperature for activation, which either decomposes the partial oxidation products, or promotes total oxidation [135g] . Previously a catalyst free and spontaneous aerobic oxidation of 1,1,2,2‐tetrakis‐( N ‐methylpyridin‐4‐ium)ethane iodide was discovered by Tcyrulnikov and co‐workers in 2018 which led to both alkene and epoxide [135h] . The first example of catalytic enantioselective autoxidation of alkenes was reported by Luo and co‐workers in 2019, using aryldiazoester 225 as a bis‐electrophile for cycloaddition with HKAs 224 (heterocyclic ketene aminals) in air for the preparation of enantioselective epoxy pyrrolidines.…”